Re: [Xen-devel] [PATCH RFC 03/18] xen/arm: allow to allocate 1/128/256/512 Mb memory chunks

[Julien Grall <julien.grall@xxxxxxx>]

Hello,

On 18/05/16 17:32, Andrii Anisov wrote:
> From: Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
>
> This is done to allow possibility of having 1 to 1 memory mapping chunks
> with size 1/128/256/512 Mb what can sagnificantly decrease time of memory
significantly

> allocation and fragmentation for 1-to-1 mapped domains.
I cannot find any patch in this series to add support for direct memory 
mapped guest.
Can you give details on why this patch would be an improvement for any 
guest and how you choose the new allocations size?
Regards,

> Signed-off-by: Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
> Signed-off-by: Iurii Konovalenko <iurii.konovalenko@xxxxxxxxxxxxxxx>
> ---
>   tools/libxc/xc_dom_arm.c | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
>
> diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
> index aeaba54..5ee8eef 100644
> --- a/tools/libxc/xc_dom_arm.c
> +++ b/tools/libxc/xc_dom_arm.c
> @@ -33,7 +33,11 @@
>   #define LPAE_SHIFT 9
>
>   #define PFN_4K_SHIFT  (0)
> +#define PFN_1M_SHIFT  (PFN_4K_SHIFT + 8)
>   #define PFN_2M_SHIFT  (PFN_4K_SHIFT+LPAE_SHIFT)
> +#define PFN_128M_SHIFT  (PFN_2M_SHIFT + 6)
> +#define PFN_256M_SHIFT  (PFN_128M_SHIFT + 1)
> +#define PFN_512M_SHIFT  (PFN_256M_SHIFT + 1)
>   #define PFN_1G_SHIFT  (PFN_2M_SHIFT+LPAE_SHIFT)
>   #define PFN_512G_SHIFT (PFN_1G_SHIFT+LPAE_SHIFT)
>
> @@ -359,11 +363,31 @@ static int populate_guest_memory(struct xc_dom_image *dom,
>           if ( rc < 0 ) break;
>           if ( rc > 0 ) continue;
>
> +        rc = populate_one_size(dom, PFN_512M_SHIFT,
> +                               base_pfn + pfn, &allocsz, extents);
> +        if ( rc < 0 ) break;
> +        if ( rc > 0 ) continue;
> +
> +        rc = populate_one_size(dom, PFN_256M_SHIFT,
> +                               base_pfn + pfn, &allocsz, extents);
> +        if ( rc < 0 ) break;
> +        if ( rc > 0 ) continue;
> +
> +        rc = populate_one_size(dom, PFN_128M_SHIFT,
> +                               base_pfn + pfn, &allocsz, extents);
> +        if ( rc < 0 ) break;
> +        if ( rc > 0 ) continue;
> +
>           rc = populate_one_size(dom, PFN_2M_SHIFT,
>                                  base_pfn + pfn, &allocsz, extents);
>           if ( rc < 0 ) break;
>           if ( rc > 0 ) continue;
>
> +        rc = populate_one_size(dom, PFN_1M_SHIFT,
> +                               base_pfn + pfn, &allocsz, extents);
> +        if ( rc < 0 ) break;
> +        if ( rc > 0 ) continue;
> +
>           rc = populate_one_size(dom, PFN_4K_SHIFT,
>                                  base_pfn + pfn, &allocsz, extents);
>           if ( rc < 0 ) break;
--
Julien Grall

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